Unit 51 Computer Systems Architecture

· Aim and purpose

To enable learners to understand the underlying architecture and components behind the functioning of computer systems.

· Unit introduction

All computer systems share the same underlying computer architecture principles. This unit examines these principles and explores the fundamentals of how computer systems work. Learners will focus on the technical detail including how the components function at an electronic level.

Learners will explore how various types of data can be represented and then stored within computer systems. This is followed by a study of the low-level system components. It includes the processor, buses and memory incorporating an analysis of how these components interact to manipulate data using the fetch-execute cycle. Low-level program instructions make up the fetch-execute cycle and simple assembly code instructions are investigated along with their interaction with the various registers that make up the Central Processing Unit (CPU). Learners will have the opportunity to develop simple programs in a low-level language.

· Learning outcomes

On completion of this unit a learner should:

1. Understand how data can be represented within computer systems
2. Understand the functions of computer system components
3. Understand the principles of processor operations.

Unit content

1         Understand how data can be represented within computer systems

Numeric data: conversions between different representations of data; representing integer numbers in different number bases; converting between number bases using integer numbers eg denary to binary, denary to hexadecimal, binary to hexadecimal; performing arithmetic operations in different number bases; representing fixed-point numbers in different number bases; representing floating-point numbers in binary

Boolean logic: logic gates; truth tables; use of logic gates in integrated circuits; logical operations eg AND, OR, NOT, NAND, NOR, XOR

Coding of data: sign and magnitude; two’s compliment; floating point; binary coded decimal; coding of character data eg ASCII (American Standard Code for Information Interchange)

Types of data: representing bit patterns for different types of data eg graphics, video, audio and other data; graphics eg bitmap (resolution, colour depth, file calculations), vector (objects, properties); sound (compression, sampling resolution, sampling rate, streaming audio, quality); video (compression, encoding, streaming, quality); analogue data; digital data; analogue signals; digital signals; data conversion eg analogue to digital; file formats eg mp3, mp4, wav, avi

2         Understand the functions of computer system components

Key components: Central Processing Unit (CPU); memory; interfaces; clock; buses, diagrammatic representation; Von Neuman architectures

Central Processing Unit: control unit; ALU (Arithmetic Logic Unit); general purpose registers; special purpose registers eg instruction pointer, accumulator; core eg single, multiple; features eg pipelining, multiprocessing, parallel processing; polling; interrupts

Memory: I/O maps; Direct Memory Access (DMA); ROM (Read Only Memory); cache; RAM (Random Access Memory) eg static, dynamic, flash

Buses: system bus; address bus; control bus; physical connections to components eg Central Processing Unit, memory, input/output (I/O) devices, system buses

Peripherals: types eg hard disc, printer, scanner, network card

3         Understand the principles of processor operations

CPU instruction sets: Reduced Instruction Set Computer (RISC); Complex Instruction Set Computer (CISC); clock rate; performance levels

Addressing: modes eg immediate; relative; address bus; addressing in the fetch-execute cycle

Machine operations: how they are organised and represented; role of the instruction decoder; low-level programs; assembly code instructions eg fetch, load, add; decision making and branching; using registers, transferring data between registers, fetch-execute cycle; program storage; data storage; addressing

Assessment and grading criteria

In order to pass this unit, the evidence that the learner presents for assessment needs to demonstrate that they can meet all the learning outcomes for the unit. The assessment criteria for a pass grade describe the level of achievement required to pass this unit.

Assessment and grading criteria
To achieve a pass grade the	To achieve a merit grade	To achieve a distinction
evidence must show that	the evidence must show	grade the evidence must
the learner is able to:	that, in addition to the pass	show that, in addition to the
	criteria, the learner is able	pass and merit criteria, the
	to:	learner is able to:
P1 explain using examples how numeric and alphanumeric data can be coded within a computer system
P2 explain using examples how different types of data can be converted and stored in computer systems
P3 convert numeric data between different number systems including floating point	M1 explain using examples how floating point numbers can be represented in binary
P4 carry out Boolean logic operations
P5 illustrate the key computer system components and how they interact
P6 explain the different types of memory that can be attached to a processor	M2 compare the roles played by different types of memory	D1 explain how the processor is physically connected to memory and input/output (I/O) devices using the system buses
P7 explain how polling and interrupts are used to allow communication between processor and peripherals

Assessment and grading criteria
To achieve a pass grade the	To achieve a merit grade	To achieve a distinction
evidence must show that	the evidence must show	grade the evidence must
the learner is able to:	that, in addition to the pass	show that, in addition to the
	criteria, the learner is able	pass and merit criteria, the
	to:	learner is able to:
P8 compare Reduced Instruction Set Computer (RISC) chips and Complex Instruction Set Computer (CISC) chips
P9 illustrate the use of the different processor registers in the fetch- execute cycle.	M3 create a low-level program which includes decision making and branching.	D2 explain how the width of the data bus and address bus affect processor performance and complexity.

Essential guidance for tutors

Delivery

It is recommended that this unit is delivered either after or in conjunction with Unit 2: Computer Systems.

Simulation software could be used extensively in this unit for example to develop learners’ understanding of logic gates and low-level programming. Other software that simulates the internal operation of the processor would also be valuable to confirm learners understanding.

Alternatively, a software application that simulates a simple CPU and an associated assembly language could be used. This type of software usually covers the basic elements of assembly language programming. Learners are able to put the theory into practice using the simulator to run programs in a controlled way, seeing all CPU activity step by step.

LO1 should be delivered using a series of worksheets to deliver the maths theory and Boolean logic operations. It’s important to link the number theory to computer activity, noting that at the lowest level binary represents the off/on nature of electricity. For example, hexadecimal is a user-friendly way of representing binary and is used in electronics and computing. Use of binary and hexadecimal in IP addressing (versions 4 and 6) could be demonstrated.

For LO2 and LO3, the CPU can be introduced as the part of the computer architecture that runs computer programs. This is facilitated by the fetch-execute cycle and this could be explained in conjunction with a simple assembly language program that, for example, adds two numbers together. This could then be used to introduce learners to the different registers that make up the CPU. The functions of the various buses and the different types of memory could then be covered.